Thermal Comfort Zone Research Articles

Establishing resilience in times of climate change—a perspective on humans and buildings

With a contribution of 40% to the annual global CO2-emissions, the built environment needs to drastically reduce its impact, while also providing pleasant and healthy indoor spaces and protecting people from weather extremes. Over time, particularly in western and industrialized countries, buildings have evolved to shield occupants almost completely from outdoor conditions. As a consequence, humans have become so used to a constant, comfortable indoor environment that we struggle to cope with thermal fluctuations. The time has come to shift perspective, as the very protective character of buildings and provision of omnipresent comfort are neither feasible nor desirable any longer. An enormous amount of energy and resources are spent to provide tightly controlled thermal environments, often with the same target temperature all year round. However, being mostly exposed to constant, comfortable indoor temperatures can have negative impacts on health and deteriorate our human capability to deal with thermal challenges. Importantly, spending time outside the thermal comfort zone is known to enhance human thermoregulatory capacities and thermal resilience, while also improving metabolic and cardiovascular health. This perspective essay aims to draw attention to novel and yet underrepresented avenues of coping with climate challenges, both with respect to the built environment and humans. Allowing more thermal variation indoors will save precious resources, decrease the negative impact of building CO2-footprints, and stimulate physiological and psychological adaptation in humans, which can lead to improved resilience and health.

Effect of quilt thermal resistance on bedding system and sleep thermal comfort

Ambient temperature and the bedding thermal resistance are two key factors affecting sleepers' thermal comfort. Six duvets with thermal resistance of 3.81, 5.12, 6.19, 7.81, 8.75 and 8.93 clo were included to investigate the effects of duvet thermal resistance on the sleep thermal comfort zone. Six males and six females were enrolled in a whole night sleep experiment, and the ambient temperature of the sleep room was adjusted to be thermally comfortable. Skin temperature, bed climate temperature and sleep stages were all acquired. Subjective evaluations including thermal perception and sleep quality were also assessed through questionnaires. The results indicated that increasing the thermal resistance of duvets widened the thermal comfort zone of ambient temperature, with the highest thermal resistance ranging from 8.2 to 17.7 °C and the lowest from 16.4 to 22.2 °C. The upper and lower temperature limits of the comfort zone did not significantly differ in their effect on sleep quality. The recommended bed climate temperature for comfortable sleep would be in the small range of 30–33 °C, and a good quality of sleep can be guaranteed in the scenario.

Thermal environment evaluation and thermal comfort zone deviation ——a case study of Chinese seaweed house in summer

Renewing the vitality of traditional ecological dwellings in the context of global carbon peaking and carbon neutrality targets has become one of the important topics in today's building sustainability research, and the evaluation of thermal comfort in traditional dwellings is the key to it. In this paper, one of the most representative ecological dwellings in the world, the “Seaweed House”, was selected as the research object. Firstly, the physical environment of a seaweed house in Dazhuang Xujia Village was measured from July 29 to August 3, 2022. Secondly, a thermal comfort questionnaire was conducted to grasp the current information of the thermal comfort in seaweed house. The results show that:1. The humidity of seaweed houses in summer is too high. 2. Residents have a thermally neutral temperature of 26.9 °C, an acceptable temperature region of (24.8–29.1 °C), and a thermally desired temperature of 25.8 °C. 3. The adaptive predicted mean vote (APMV) model suitable for thermal comfort evaluation of seaweed houses was developed. The results of the study provide a precise theoretical guide for the study of thermal comfort evaluation models in this region, and a useful reference for the study of the renewal and renovation of the seaweed houses.

A Novel Molecular PCM Wall with Inorganic Composite: Dynamic Thermal Analysis and Optimization in Charge-Discharge Cycles.

The combination of electric heating and thermal energy storage (TES) with phase change material (PCM) can achieve load shifting for air conditioning energy saving in building sectors. Their non-flammability, relatively good mechanical properties, and low cost make inorganic PCMs attractive in construction engineering. However, PCMs often show poor thermal conductivity, low heat transfer efficiency, leakage risk, etc., in applications. Moreover, the practical thermal performance of PCM-TES sometimes fails to meet demand variations during charge and discharge cycles. Therefore, in this study, a novel integrated electric PCM wall panel module is proposed with quick dynamic thermal response in space heating suitable for both retrofitting of existing buildings and new construction. Sodium-urea PCM composites are chosen as PCM wall components for energy storage. Based on the enthalpy-porosity method, a mathematical heat transfer model is established, and numerical simulation studies on the charge-discharge characteristics of the module are conducted using ANSYS software. Preliminary results show that the melting temperature decreases from 50 °C to approximately 30 °C with a 30% urea mixing ratio, approaching the desired indoor thermal comfort zone for space heating. With declining PCM layer thickness, the melting time drops, and released heat capacity rises during the charge process. For a 20 mm thick PCM layer, 150 W/m2 can maintain the average surface temperature within a comfort range for 12.1 h, about half the time of a 24 h charge-discharge cycling periodicity. Furthermore, placing the heating film in the unit center is preferable for improving overall heat efficiency and shortening the time to reach the thermal comfort temperature range. This work can provide guidance for practical thermal design optimization of building envelopes integrated with PCM for thermal insulation and energy storage.

A methodological approach to evaluate the passive cooling effect of Oasis palm groves

With climate change and the recurring heat waves in arid lands, human well-being and activities in oasis settlements can be critical subjects for the ongoing years. This paper introduces a methodological approach to investigate the potential passive cooling effect inside the oasis palm groves, their spatial characteristics, and microclimatic thresholds. Based on the Physiological Equivalent Temperature (PET) index, the paper evaluates oasis palm groves’ ability to ensure a neutral human outdoor thermal comfort zone. The research aims to determine guidance of an optimal and nearly optimal thermal comfort threshold based on a series of parametric scenarios of oasis configurations. The study provides a cross of 12 ideal oasis scenarios. The paper evaluates the oasis cooling effect and thermal comfort and recommends aligning urban planning with thermal thresholds. Results reveal that PET neutral zone can be assured into ranges of 29°C to 37°C, 19°C to 20°C, 55% to 58%, and 1m/s to 2m/s of mean radiant temperature, air temperature, relative humidity and air velocity, respectively. The results refer policymakers and urban planners to invest in the passive cooling effect of the oasis palm grove in future urban design strategies to maintain the maximum neutral comfort hours during heat waves.

An experimental study of thermal comfort zone extension in the semi-open spray space

Pedestrians will experience different heat stress stages from sunlight to semi-open spray space as they shuttle through stations with spray systems. There are few studies on the influence of thermal experience and thermal history of this specific environment on pedestrian thermal comfort. This study explored the dynamic physiological thermal response and thermal perception of humans in the sunlight to semi-open spray space in Qingdao, China. Meteorological and physiological parameters were measured and questionnaires were conducted. The results showed that from outdoor sunlight to semi-open spray space, thermal sensation and thermal comfort were improved, the mean skin temperature of the whole body decreased by 0.5 °C, the neutral standard effective temperature (NSET*) enhanced by 8.8 °C, and the NSET* range (NSET*R) increased by 7.3–10.2 °C. However, after 10 min in the semi-open spray space, the thermal comfort gradually deteriorated. In addition, the main meteorological factors affecting the thermal sensation in sunlight and semi-open spray space were air temperature and mean radiant temperature, and the main physiological factor was the skin temperature of the right upper arm. This study is helpful for the operation design of spray systems and the evaluation of the thermal environment in semi-open spray in cities.

Effective Moisture Temperature: Ventilation performance index accounting for effects of air temperature and relative humidity on thermal comfort

Relative humidity could be a predominant parameter for thermal comfort. The existing ventilation performance index regarding thermal comfort, i.e., the Effective Draft Temperature (EDT), does not account for the effect of relative humidity on thermal comfort. This study proposes a novel ventilation performance index, i.e., the Effective Moisture Temperature (EMT), to account for the effects of air temperature and relative humidity on thermal comfort. The proposed EMT is defined as an analogy of the EDT and is quantified by the theoretical analysis of the thermal neutrality, boundaries of thermal comfort zone, and equivalent transfer between the relative humidity and air temperature. The proposed EMT is tabulated for practical convenience under cooling and heating scenarios with different thermal comfort requirements. The results based on Monte Carlo simulations and ASHRAE Global Thermal Comfort Database II show that for the low air movement conditions, the accuracy of the original EDT is 23.8%–88.0%, while the accuracy of the proposed EMT is 98.6%–99.5%. This study further develops the Effective Draft and Moisture Temperature (EDMT) for elevated air movement by integrating the EMT and the cooling effect of air movement. For the elevated air movement conditions, the accuracy of the extended EDT is 84.1%–95.5%, while the accuracy of the proposed EDMT is 96.7%–99.2%. The proposed EMT and EDMT contribute to developing thermally comfortable built environments.

A kirigami-enabled electrochromic wearable variable-emittance device for energy-efficient adaptive personal thermoregulation.

For centuries, people have put effort to improve the thermal performance of clothing to adapt to varying temperatures. However, most clothing we wear today only offers a single-mode insulation. The adoption of active thermal management devices, such as resistive heaters, Peltier coolers, and water recirculation, is limited by their excessive energy consumption and form factor for long-term, continuous, and personalized thermal comfort. In this paper, we developed a wearable variable-emittance (WeaVE) device, enabling the tunable radiative heat transfer coefficient to fill the missing gap between thermoregulation energy efficiency and controllability. WeaVE is an electrically driven, kirigami-enabled electrochromic thin-film device that can effectively tune the midinfrared thermal radiation heat loss of the human body. The kirigami design provides stretchability and conformal deformation under various modes and exhibits excellent mechanical stability after 1,000 cycles. The electronic control enables programmable personalized thermoregulation. With less than 5.58 mJ/cm2 energy input per switching, WeaVE provides 4.9°C expansion of the thermal comfort zone, which is equivalent to a continuous power input of 33.9 W/m2. This nonvolatile characteristic substantially decreases the required energy while maintaining the on-demand controllability, thereby providing vast opportunities for the next generation of smart personal thermal managing fabrics and wearable technologies.

Seasonal thermal comfort and adaptive behaviours for the occupants of residential buildings: Shaoxing as a case study

This study aimed to investigate the thermal comfort requirements in residential buildings and establish an adaptive thermal comfort model. A two-year field study was conducted on residential buildings in Shaoxing, Zhejiang Province, China. A total of 172 apartments (187 people) were surveyed, and 2400 valid questionnaires on thermal sensation from residents were obtained in two years. The results showed that the thermal comfort requirements of residents change with the seasons: Different seasons lead to changes in the range of thermal comfort zones and the residents’ thermal adaptation models, which are related to the climatic characteristics of each season. Compared with the traditional year-round adaptive thermal comfort model, seasonal models could reflect the status of the residents’ thermal adaptation caused by the characteristics of dynamic climate change more comprehensively and accurately. In addition, this study determined the residents’ psychological and behavioural adaptability to the seasons and found the characteristics of thermal sensation and requirements for thermal comfort in different seasons. In conclusion, this study provides people in the study area with basic knowledge of their thermal comfort requirements. The results could be used as a basis to improve energy efficiency and meet comfort needs in the future.

A quantitative evaluation model of outdoor dynamic thermal comfort and adaptation: A year-long longitudinal field study

The understanding of human outdoor thermal comfort demand and thermal adaptation contributes to sustainable urban design as well as city resilience in the context of human health and wellbeing. Humans' past thermal experience influence their outdoor thermal comfort. However, the quantitative relationship between the past thermal experience and outdoor thermal comfort is still not clear. This study aims to reveal quantitative relations of the impact of people's past thermal experience on adaptive thermal comfort and to develop a new outdoor adaptive thermal comfort model. A year-long longitudinal questionnaire survey along with a combination of outdoor thermal environment campaigns was carried out in Chongqing, China. It began on August 15, 2020, and finished on August 19, 2021. Through the analysis of 2240 valid responses to the questionnaire survey, the outdoor thermal adaptation characteristic and dynamic thermal comfort evaluation of the respondents were revealed. The results show that the quantified temperature of past outdoor thermal experience is the quadratic correlation with the thermal sensitivity coefficient and deviation constant, and the linear correlated with outdoor thermal demands. Based on the quantitative analysis, a new outdoor adaptive thermal comfort model has been developed as a function of the exponentially weighted sum of historical mean air temperature series (MeanTrm). The outdoor adaptive thermal comfort zones by 80% and 90% satisfactions thereby have been first drawn based on the Universal Thermal Climate Index (UTCI). The study developed a methodology for the evaluation of dynamic outdoor thermal comfort which can be used for different climate regions.

Thermal stress impaired expression of insulin-like growth factor binding proteins in pigs

This study aimed to investigate the correlation of IGFs, IGFBPs, and IGFBPRs of grower pigs with change in temperature humidity index (THI). THI was calculated to know the months of the year when pigs feel discomfort and samples of feed offered were analyzed to know the nutritional availability/deficit. The calculated average THI was above thermal comfort zone for seven months in a year. It was observed that crude protein (CP) and metabolizable energy (ME) availability to pigs were deficient. Gilts of two months age and similar body weight were randomly divided into two groups (n=6); viz. Con-fed animals (feed offered by the farmer) and For-fed animals (formulated feed supplement + Con-fed). The composition of formulated feed supplement was dried leaf of Moringa oleifera, soybean meal, rice mill waste, and mineral mixture. The plasma cortisol level increased in the experimental animals with accelerated THI as evidenced by the strong positive correlation of THI with HSP70 and HSP90. The level of leptin and ghrelin did not have significant relation with the expression level of HSPs in the present study, however, in the control animals, a low level of leptin was observed. The correlation between the growth factors and HSPs was not significant. During the season, where the THI was above the thermal comfort zone, the IGFBPR and IGFBP concentrations were non-significantly increased along with the increased THI.

Identification of climate change impact and thermal comfort zones in semi-arid regions of AP, India using LST and NDBI techniques

Andhra Pradesh, in southern India, frequently experiences warm summers and winters. However, the year-round greater relative humidity and the positioning of the summer hot spots are linked to actual weather heat exhaustion during the warmest months. Climate change is a significant—and frequently disregarded—factor in the relationship between climate and mortality. With the use of the Land Surface Temperature (LST) and Normalized Difference Built-up Index (NDBI), we sought to identify the climatic change in this research. Additionally, we attempted to identify the Thermal Comfort Zones (TCZs) in Andhra Pradesh, South India's semi-arid regions. Arc GIS and ERDAS Imagine were used to process the satellite data of Landsat 4–5 (TM & MSS), Landsat 7 ETM+, and Landsat 8 OLI for the development of LST and NDBI. The research was conducted for the past thirty years from 1990 to 2020. The resultant thermal comfort zones map was classified into four zones, Zone - I (Safe zone), Zone – II (Moderately safe zone), Zone – III (Risk Zone), and Zone -IV (Highly Risk Zone). The relation between the LST and NDBI is also revealed using correlation regression analysis in the study region. It has been noted that urban centre and high-density regions had greater LST than rural locations. The study finds that although this differs from one ecological zone to another and the distribution of LST intensity in the urban area depends on its changing LULC, various types of land cover within an urban region might impact the spatial pattern of urban LST. The main conclusions of this study might help policymakers understand the need of enabling more sustainable urban development in cities.

Bioclimatic zoning for quails in the rain season in the state of Paraíba, Brazil

This work aimed to perform bioclimatic zoning based on the temperature and humidity index (THI) for quails from the 3rd to the 5th week of life during the rainy season in the state of Paraíba, Brazil, in order to identify the most suitable mesoregions among the Zona da Mata, Agreste, Borborema and Sertão for the breeding of these birds and to propose mitigating measures for the thermal comfort of the animals. The monthly air temperature and relative humidity data for calculating the THI were obtained from conventional meteorological stations of the National Meteorological Institute of the Brazilian federal government from 1961 to 2015, in turn making maps with the spatial distribution of the index. The index ranged from 71 to 76 in the various mesoregions of Paraíba, with Agreste being the best mesoregion for breeding quails from the 3rd to the 5th week of life, thus providing a thermal comfort zone for birds and only requiring a few corrective measures in their facilities, when necessary, followed by the Sertão, Zona da Mata and Borborema mesoregions.

Recent Advances in Thermoregulatory Clothing: Materials, Mechanisms, and Perspectives.

Personal thermal management (PTM) is a promising approach for maintaining the thermal comfort zone of the human body while minimizing the energy consumption of indoor buildings. Recent studies have reported the development of numerous advanced textiles that enable PTM systems to regulate body temperature and are comfortable to wear. Herein, recent advancements in thermoregulatory clothing for PTM are discussed. These advances in thermoregulatory clothing have focused on enhancing the control of heat dissipation between the skin and the localized environment. We primarily summarize research on advanced clothing that controls the heat dissipation pathways of the human body, such as radiation- and conductance-controlled clothing. Furthermore, adaptive clothing such as dual-mode textiles, which can regulate the microclimate of the human body, as well as responsive textiles that address both thermal performance (warming and/or cooling) and wearability are discussed. Finally, we include a discussion on significant challenges and perspectives in this field, including large-scale production, smart textiles, bioinspired clothing, and AI-assisted clothing. This comprehensive review aims to further the development of sustainably manufactured advanced clothing with superior thermal performance and outstanding wearability for PTM in practical applications.

Cooling effect of air movement of advanced air distribution under heating mode: Experimental analyses of stratum ventilation

The cooling effect of air movement significantly affects the energy-efficient provision of thermal comfort with advanced air distribution. Existing studies merely focus on the cooling effect of air movement under cooling mode. However, the cooling effect of air movement under heating mode can be different from that under cooling mode. This is because the cooling effect of air movement negatively and positively affects thermal comfort under heating and cooling modes respectively. This study experimentally investigates the cooling effect of air movement of stratum ventilation under heating mode. Stratum ventilation is representative of advanced air distribution with significant air movement for a proper airflow pattern under heating mode. A wide range of thermal conditions are tested with the air temperature of 19 °C–25 °C and air velocity of 0.1 m/s – 1.2 m/s. The thermal sensation votes and percentages of dissatisfied are simultaneously surveyed. Based on the experimental data, the cooling effect of air movement under heating mode is quantified, which is higher and lower than that under cooling mode in the cool and warm thermal environments respectively. Moreover, based on the upper and lower boundaries determined according to the percentage of dissatisfied of 10% predicted by an optimized model, the thermal comfort zone is prescribed under heating mode. For the thermal comfort zone, the cooling effect of air movement is compensated by the enhanced air temperature. This study contributes to improving the heating performances of advanced air distribution with the cooling effect of air movement.

A thermal comfort evaluation on vehicular environments based on local human body thermal sensations

With the rapid development of the automobile industry and increasing demand for automobiles, consumers also have more and more car requirements. They do not only consider energy, safety and price but also expect a good indoor environment and improved thermal comfort. In order to construct and apply a thermal comfort evaluation method suitable for Chinese consumers, a relationship between the equivalent space temperature and the thermal sensation was obtained by collecting characteristic thermal sensation data of the human body in different environments. An evaluation method based on whole-body and local thermal comfort sensation characteristics for adult Chinese males and females was designed, At the same time, the study found that women's tolerance for thermal sensation is lower and the thermal comfort zone is relatively smaller. In order to explore the accuracy of the evaluation method and a typical non-uniform vehicular environment was selected to verify the findings. The local and whole-body equivalent space temperature of the co-driver seat in the vehicle was tested with a warm dummy, through which whole-body and local thermal sensation values were predicted. The local and whole-body thermal sensation was tested with subjects' subjective experience under the same conditions. The predicted thermal sensation obtained through the equivalent space temperature was compared to the subjective experience results, and the correlation reached up to 0.911, while significance (two-tailed) only reached 0.002, it was possible to predict the thermal sensation vote within an accuracy level of 0.3 point, further proving the accuracy of the whole-body and local thermal comfort evaluation method for adult Chinese male thermal sensation characteristics as proposed in this paper. The results obtained in this study can be used to predict environmental thermal comfort.

Application potential analysis of different control strategies for radiant floor cooling systems in office buildings in different climate zones of China

The application potential of radiant floor cooling systems is affected by climatic conditions. The meteorological parameters of 22 cities in five climatic zones in China (severe cold (SC), cold, hot summer and cold winter (HSCW), hot summer and warm winter (HSWW), and temperate) are analyzed to evaluate the applicability of four conventional control strategies of radiant floor cooling system in office buildings. The control strategies are modeled in the Transient System Simulation Program (TRNSYS), and the indoor thermal comfort, condensation risk, energy consumption, and carbon emissions are analyzed. Multi criteria decision-making is used to evaluate the radiant floor system. The results show that the control strategy with direct ground cooling produces the highest energy savings in the five climate zones. The energy savings are 25–66 % higher than those of the three control strategies using a heat pump as a cold source. Under the same indoor environment conditions, the three-step control strategy provides the optimum indoor temperature and humidity control. The number of hours when the three-step control strategy exceeds the thermal comfort zone is 5 % in 22 cities, and the number of hours with condensation risk is only 3%. The variable water supply temperature control and precooling control have better performance than the other strategies in the SC, cold, and temperate zones. In addition, the control strategies are ranked based on their application potential in 22 cities. The application potential of the radiant floor cooling system with a direct ground cooling source is the highest in the five climate zones in the two scenarios with equal weights of the four criteria and is preferable due to less carbon emissions. When the condensation risk is considered, the radiant floor cooling system with a direct ground cooling source exhibits better performance in the SC and cold zones. The variable water supply temperature control is the optimum strategy in the HSCW, HSWW, and temperate zones. The precooling control strategy ranks the highest in Changchun and Guiyang, and the three-step control strategy performs the best in Shanghai.

Field Assessment of The Indoor Thermal Environment and Thermal Comfort Levels for Naturally Conditioned Residential Buildings in The Tropical Climate

As we spend most of our time in indoor spaces, half of the energy consumption in buildings is used to improve the indoor thermal environment to achieve thermally comfortable conditions. However, studies showed that people in naturally ventilated buildings have a broader thermal comfort zone. Additionally, people in hot areas can tolerate higher indoor temperatures. Therefore, this work investigates and evaluates the indoor thermal environment and the thermal comfort level in naturally conditioned buildings. Field measurements were conducted in various residential spaces in different buildings. The measurements were used to calculate the operative temperature (Tₒₚ), which was utilized to evaluate the thermal comfort level based on the adaptive models and taking into account the effect of the various orientations. The results showed that maximum Tₒₚ ranged between 27.70 ℃ and 35.50 ℃, depending mainly on the space’s orientation. Additionally, the thermal discomfort time ranged between 0% and 73%. The South & East, Southeast, South, and East orientation were more critical during the study period, while the North, Northeast, and Northwest orientations achieved better indoor thermal conditions. However, these results can vary throughout the year, depending on the sun’s path. This study revealed that the daily average heat gain to the building from the Southeast and South orientations is higher than that from the East and West orientations due to the longer exposure time to solar radiation.

Study of the thermal comfort and the energy required to achieve it for housing modules in the environment of a high Andean rural area in Peru

This study mainly evaluates and analyzes the thermal comfort of the young inhabitants of Imata, a high Andean rural village located at 4500 m of altitude in southern Peru. Acceptable thermal comfort ranges are defined for the villagers, from face-to-face surveys and with a device implemented for this study, which allows recording the temperature, relative humidity, clothing, and the thermal sensation vote TSV (considering a five-point thermal sensation scale). The comfort ranges are determined from the mean and standard deviation of each set of TSV values. Four thermal comfort zones are proposed, which are plotted on the psychrometric chart. Further, two experimental housing modules (M1 and M2) are analyzed, which were built in Imata with passive solar heating strategies. The simulation of both modules with m2m software allows determining the indoor temperatures for the year 2019 and the comfort schedules inside the modules by considering the comfort ranges established in this study. Finally, the energy required to achieve thermal comfort inside M1 and M2 is estimated using the simplified method of the ISO 13790 Standard.

Investigation of Thermal Adaptation and Development of an Adaptive Model under Various Cooling Temperature Settings for Students’ Activity Rooms in a University Building in Malaysia

The use of an air conditioner (AC) becomes essential, particularly in a hot and humid climate, to provide a comfortable environment for human activities. The setpoint is the agreed temperature that the building will meet, and the use of the lowest setpoint temperature to accelerate the cooling of indoor spaces should be avoided. A comprehensive field study was conducted under various cooling temperature settings in two student activity rooms in a university building in Malaysia, so as to understand respondents’ characteristics and behavior toward AC usage, to estimate the comfort at various indoor temperatures, to develop an adaptive model of thermal comfort in AC spaces, and to compare the comfort temperature with related local and international indoor thermal environmental standards. The findings indicated that water intake and clothing insulation affected personal thermal comfort. Moreover, the mean comfort temperature for respondents was 24.3 °C, which is within an indoor thermal comfort zone of 23–27 °C. The findings suggest that the preference of occupants living in a hot and humid region for lower temperatures means that setting temperatures lower than 24 °C might underestimate the indoor comfort temperature. Additionally, an adaptive relationship can be derived to estimate the indoor comfort temperature from the prevailing outdoor temperature.